Revealing the hidden dynamics of confined water in acrylate polymers: Insights from hydrogen-bond lifetime analysis

Polymers contain functional groups that participate in hydrogen bond (H-bond) with water molecules, establishing a robust H-bond network that influences bulk properties. This study utilized molecular dynamics (MD) simulations to examine the H-bonding dynamics of water molecules confined within three poly(meth)acrylates: poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(1-methoxymethyl acrylate) (PMC1A). Results showed that H-bonding dynamics significantly slowed as the water content decreased. Additionally, the diffusion of water molecules and its correlation with H-bond breakage were analyzed. Our findings suggest that when the H-bonds between water molecules and the methoxy oxygen of PMEA are disrupted, those water molecules persist in close proximity and do not diffuse on a picosecond timescale. In contrast, the water molecules H-bonded with the hydroxy oxygen of PHEMA and the methoxy oxygen of PMC1A diffuse concomitantly with the breakage of H-bonds. These results provide an in-depth understanding of the impact of polymer functional groups on H-bonding dynamics.Comment: 11 pages, 8 figures for main text, 10 pages for supplementary material, to appear in J. Chem. Phy

Diffusion-Controlled Recrystallization of Water Sorbed into Poly(meth)acrylates Revealed by Variable-Temperature Mid-Infrared Spectroscopy and Molecular Dynamics Simulation.

Recrystallization behaviors of water sorbed into four poly(meth)acrylates, poly(2-methoxyethyl acrylate), poly(tetrahydrofurfuryl acrylate), poly(methyl acrylate), and poly(methyl methacrylate), are investigated by variable-temperature mid-infrared (VT-MIR) spectroscopy and molecular dynamics (MD) simulation. VT-MIR spectra demonstrate that recrystallization temperatures of water sorbed into the polymers are positively correlated with their glass-transition temperatures reported previously. The present MD simulation shows that a lower-limit temperature of the diffusion for the sorbed water and the glass-transition temperatures of the polymers also have a positive correlation, indicating that the recrystallization is controlled by diffusion mechanism rather than reorientation mechanism. Detailed molecular processes of not only recrystallization during rewarming but also crystallization during cooling and hydrogen-bonding states of water in the polymers are systematically analyzed and discussed

Adsorption Energetics of Amino Acid Analogs on Polymer/Water Interfaces Studied by All-Atom Molecular Dynamics Simulation and a Theory of Solutions

Energetics of adsorption was addressed with all-atom molecular dynamics simulation on the interfaces of poly(2-methoxyethyl acrylate) (PMEA), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) with water. A wide variety of adsorbate solutes were examined, and the free energy of adsorption was computed with the method of energy representation. It was found that the adsorption free energy was favorable (negative) for all the combinations of solute and polymer, and among PMEA, PMMA, and PBA, the strongest adsorption was observed on PMMA for the hydrophobic solutes and on PMEA for the hydrophilic ones. According to the decomposition of the adsorption free energy into the contributions from polymer and water, it was seen that the polymer contribution is larger in magnitude with the solute size. The total free energy of adsorption was correlated well with the solvation free energy in bulk water only for hydrophobic solutes. The roles of the intermolecular interaction components such as electrostatic, van der Waals, and excluded-volume were further studied, and the electrostatic component was influential only in determining the polymer dependences of the adsorption propensities of hydrophilic solutes. The extent of adsorption was shown to be ranked by the van der Waals component in the solute-polymer interaction separately over the hydrophilic and hydrophobic solutes, with the excluded-volume effect from water pointed out to also drive the adsorption.Nobuhiro Yasoshima, Tatsuya Ishiyama, and Nobuyuki Matubayasi. Adsorption Energetics of Amino Acid Analogs on Polymer/Water Interfaces Studied by All-Atom Molecular Dynamics Simulation and a Theory of Solutions. The Journal of Physical Chemistry B 2022, 126, 4389-4400, DOI: 10.1021/acs.jpcb.2c01297

Diffusion-Controlled Recrystallization of Water Sorbed into Poly(meth)acrylates Revealed by Variable-Temperature Mid-Infrared Spectroscopy and Molecular Dynamics Simulation

Recrystallization behaviors of water sorbed into four poly­(meth)­acrylates, poly­(2-methoxyethyl acrylate), poly­(tetrahydrofurfuryl acrylate), poly­(methyl acrylate), and poly­(methyl methacrylate), are investigated by variable-temperature mid-infrared (VT-MIR) spectroscopy and molecular dynamics (MD) simulation. VT-MIR spectra demonstrate that recrystallization temperatures of water sorbed into the polymers are positively correlated with their glass-transition temperatures reported previously. The present MD simulation shows that a lower-limit temperature of the diffusion for the sorbed water and the glass-transition temperatures of the polymers also have a positive correlation, indicating that the recrystallization is controlled by diffusion mechanism rather than reorientation mechanism. Detailed molecular processes of not only recrystallization during rewarming but also crystallization during cooling and hydrogen-bonding states of water in the polymers are systematically analyzed and discussed